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[TowerTalk] Coax Rating

To: <towertalk@contesting.com>
Subject: [TowerTalk] Coax Rating
From: i4jmy@iol.it (i4jmy@iol.it)
Date: Thu, 1 Mar 2001 14:57:00 +0100
The reason why an RG8X insn't raccomandable at high power levels is 
because of a shield that's made of a thin aluminum Foil-Polyester Tape-
Aluminum Foil and only very few thin copper wires as braid shield.
The foam dielectric hasn't significant losses and a foam cable of the 
same size of an RG8X, but with a classic copper braid or a more 
consistent foil (aluminium or copper), would safely withstand much more 
than US legal power at 7 MHz, and roughly twice the power of an RG58 
expecially at 30 MHz and above.

73,
Mauri I4JMY


> ---------- Initial message -----------
> 
> From    : owner-towertalk@contesting.com
> To      : <towertalk@contesting.com>
> Cc      : 
> Date    : Thu, 1 Mar 2001 08:35:18 -0500
> Subject : RE: [TowerTalk] Coax Rating
> 
> 
> Ted,
> 
> Be careful.  Yes, I have had a meltdown as you call it, using some
> hamfest-grade RG8X on a 100 ft run feeding a 1/2 wave on 40.  The 
power into
> the feed line was likely about 700W.   I don't know whether this 
happened
> while operating on 40 or 15.  And here's the caution...you might 
squeak thru
> with a perfectly flat SWR.  But with 3/2 waves I'd bet you will not 
have
> that.  Any SWR will significantly increase the probability of zapping 
the
> line.
> 
> As I recall, the rating is about 300V across that foam dielectric.  
Less
> sure of that than the above. I believe RG58 is actually more 
forgiving than
> RG8X in terms of power handling.
> 
> I'm using RG8 now, with a convenient tree to help support the weight 
so the
> antenna doesn't have to see it all.
> 
> 73/Gary W2CS
> 
> 
> | -----Original Message-----
> | From: owner-towertalk@contesting.com
> | [mailto:owner-towertalk@contesting.com]On Behalf Of Ted & Joyce 
Wilhelm
> | Sent: Wednesday, February 28, 2001 11:39 PM
> | To: towertalk@contesting.com
> | Subject: [TowerTalk] Coax Rating
> |
> |
> | Am planning on trying to put up 3  1/2 waves on 40mtrs. and wonder 
if
> | anyone knows the maximum power that RG8X will handle on a relatively
> | short run less than 100 feet....I know I would probably be better 
off
> | with something like 213 or the like but am concerned with the weight
> | factor....Anyone had any major meltdowns using the lighter feed 
line.
> | Thanks,
> | Ted    K9HUH



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